At least two unlicensed spectrums have been allocated by the Federal Communication Commission (FCC) for high data-rate wireless communication. One is the Ultrawideband (UWB) standards, with a 7.5 GHz bandwidth, and the other is the 60 GHz standards, with a 7 GHz bandwidth. There has been strong industry interest in both of these spectrums.
One problem or speed “bottleneck” presently precluding full utilization of these wide bandwidths lies in the implementation of the Analog to Digital converter (ADC). A 7 GHz transmission bandwidth means a minimum Nyquist sampling rate of 14 G samples per second to prevent signal from aliasing. ADCs that can sample at such ultra-high speeds are not yet commercially available or even presently contemplated using any economic semiconductor technology. As a result, the industry is using either some variations of pulsed transmission, or only a limited narrow bandwidth for transmission. Neither of these techniques makes full use of the available broad bandwidths.
The concept of a concurrent receiver might help to relieve these issues. As described in U.S. Pat. Nos. 6,674,337 and 6,917,815 to Hashemi et al., an incoming signal is first divided into two narrow bandwidths, each of them accessible to an ADC, so that both are received at the same time (concurrently). The major disadvantages of these inventions are: 1) the two frequencies are pre-selected, and 2) the architecture is not scalable. Also, these inventions are not scalable in terms of the number of outputs and frequency plan.
There is a need for a concurrent filter that lends itself to scalability and that permits real time reconfiguration.